If you decide on a close alignment with Mastodon, then you should be aware of places where Mastodon - as the early adopter and leading project on the Fediverse - made implementation choices to fill in blanks of the AP specification, that are less desirable to be kept around as the fediverse evolves.
Many AP devs, out of convenience, model their projects on Mastodon concepts and code, and with that are deviating from directions that the spec authors (Christopher Lemmer Webber et al) intended the specs to evolve. Most prominent choice here is to support the Mastodon API for client interaction, instead of implementing a spec-compliant AP Client 2 Server API.
Just a heads up, as I am not in the know of the full technical intricacies you may encounter. The true danger is a split in the Fediverse with one part following the Mastodon way, and the other part following the specs.